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Cosmology Research in China

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ECL 2018 Autumn Workshop
Presentation by Prof. Xuelei Chen
National Astronomical Observatories,
Chinese Academy of Sciences, China

Published in: Science
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Cosmology Research in China

  1. 1. Cosmology Research in China Xuelei Chen National Astronomical Observatories, Chinese Academy of Sciences xuelei@cosmology.bao.ac.cn ECL Autumn workshop2018 Remote Talk 2018.10.03
  2. 2. Outline of my talk  Introduction  Major Institutions (Universities & Chinese Academy of Science)  Existing Facilities and Science Highlights:  simulations  optical telescopes (LAMOST)  radio telescopes (FAST, 21CMA, Tianlai(XC))  space mission(DAMPE), dark matter search(PandaX) & Cosmic Ray  Planned Facilities  AliCPT  space telescope  Discovering Sky at Longest wavelength (XC)  Conclusion
  3. 3. Introduction: Cosmological Problems • Dark Matter • Dark Energy • Origin of the Universe • Structure Formation • Observational Probes: Cosmic microwave background (CMB), large scale structure (LSS): galaxy surveys, 21cm, gravitational lensing, ...
  4. 4. Universities Beijing: Peking Univ. (& KIAA): lensing, quasar; Tsinghua Univ.: galaxy formation, supernova, reionization, WIMP search; Beijing Normal Univ.: gravitational wave, Hubble parameter Shanghai: Shanghai Jiaotong Univ.: large scale structure (simulation, lensing, galaxy formation, SZ effect and peculiar velocities, ...), WIMP direct search Hefei: USTC (theory, optical observation) Guangzhou: Sun Yatsun Univ.: gravitational wave, dark energy theory Nanjing: Nanjing Univ.: galaxy formation, dark matter indirect search Xiamen Univ., Yunnan Univ., ......
  5. 5. Chinese Academy of Science Observatories (running most facilities): •NAOC(Beijing): dark matter & dark energy, simulation, 21cm cosmology, FAST, LAMOST, space telescope, + ...... •SHAO(Shanghai): SKA, VLBI •Purple Moutain Observatory (PMO,Nanjing): Antarctica astronomy, DAMPE, sub-mm •Yunnan Observatory (Kunming): stellar evolution, solar astronomy •Xinjiang Observatory (Urumuqi): pulsar, radio astronomy Other Related Insitiutes: •Institute of High Energy Physics(IHEP, Beijing): quintom model,CMB(AliCPT), neutrino experiment, cosmic ray experiment (LHAASO), X-ray space missions •Institute of Theoretical Physics(ITP, Beijing): theoretical models, gravitational wave University of Chinese Academy of Science (UCAS)
  6. 6. Astronomical Facilities in China Beijing Shanghai Nanjing Sichuan Yunnan Guizhou Xinjiang Inner M ongolia Tibet LAMOST Tianlai 21CMA FAST AliCPT Hefei Guangzhou
  7. 7. Numerical Simulations Rank Name Rmax PFLOPS Vendor year Site 1 Summit 122.3 IBM 2018 Oak Ridge Lab, USA 2 Sunway Taihu Light 93.015 NRCPC 2016 NSC Wuxi, China 3 Sierra 71.61 IBM 2018 Lawrence Livermore, USA 4 Tianhe-2A 61.445 NUDT 2013 NSC Guangzhou, China 5 Al Bridging Cloud Infrastructure 19.88 Fujitsu 2018 NIAIST, Japan Top 500 List (June 2018)
  8. 8. Tiannu simulation(T.-J. Zhang, BNU): (3 x 1012 particles), and new method of meausuring neutrino massH. Yu et al., Nature Astronomy, 1, 0143(2017) Some Simulation Results ELUCID (Yipeng Jing, Xiaohu Yang, SJTU) constrained simulation: 30723 particles, 500 Mpc box F. Shi et al., ApJ 861, 137 (2018) L. Gao’s group (NAOC): work with the MPA and Durham groups on simulations (Millenium, Phoenix, Aquarius, ...)
  9. 9. Existing Facilities - Optical TelescopesExisting Facilities - Optical Telescopes 2.16-m Telescope @Xinglong2.4-m Telescope @Yunnan 60/90cm Schmidt @Xinglong 100/120cm Schmidt Telescope @Xuyi (near Nanjing) Solar Tower @Beijing Guo Shoujing Telescope (LAMOST) @Xinglong (near Beijing) Antarctica 50cm @Dome A
  10. 10. LAMOST focal plane fiber positioning Ma: 5.72m×4.4m, Mb: 6.67m×6.05m Clear aperture: 4m Field of view: 5° Number of fibers: 4000 Spectral ranges: 370-900nm Spectral resolution: R=500, 1000, 1500 Limit magnitude: 20.5m (1.5h, R=500) Observable sky: -10°to +90° Declination Originally designed for galaxy survey, now primarily works on stellar suverys
  11. 11. Science Highlights • Stellar kinematics: Measurement of Milky Way rotation curve Vc(R0)=240±6 km/s, Mh=0.9x10±0.08 x 1012 M⊙ ρlocal= 0.0083±0.0005M⊙pc-3 • Local DM density ρlocal= 0.018±0.005 M⊙pc-3 =0.68 GeV cm-3 • Puzzling high Li abundance in metal poor low mass red giants Y. Huang et. al., 2016, MNRAS 463, 2623 Q. Xia et. al., 2016, MNRAS 458, 3839 H. Li et. al., 2018, ApJL852, 31
  12. 12. SDSS eBOSS data – baryon acoustic oscillation (BAO) G.-B. Zhao et al., 2017, MNRAS 466, 762 SDSS DR12 Dynamical Dark Energy (3.5σ)? G.-B. Zhao et al., 2017, Nature Astronomy, 1,627
  13. 13. Existing Facilities - Radio TelescopesExisting Facilities - Radio Telescopes 50m @ Beijing 40m @ Yunnan 25m @ Xinjiang 13.7m Sub-mm Telescope Tianma 65 @Shanghai Solar Radio (MUSER) 40x4.5m + 60x2m @ Inner Mongolia FAST 500m @Guizhou 21CMA @Xinjiang 80 stations Tianlai @Xinjiang 3 x15mx40m cylinder + 16 x 6m dish
  14. 14. Five-hundred-meter Aperture Spherical Telescope - FAST FAST innovation points: •Unique Karst depression as the site •Active main reflector •Cable - parallel robot feed support FAST Science Cases: •Neutral Hydrogen line (HI) survey • Pulsar research • Molecular lines • Joining VLBI network • Search for Extraterrestrial Intelligence (SETI) Construction completed in September 2016. So far ~50 pulsars found during commissioning.
  15. 15.  Reflector: R ~ 300m, D ~ 500m, opening angle: θ ~ 110-120°  Illuminated aperture: Deff=300m  Sky coverage: maximum zenith angle 40°  Working frequencies: 70MHz-3GHz  Sensitivity 2000 ㎡ /K  Resolution 2.9’ ,  Pointing Accuracy : 8″  Multibeam 19 Optical Geometry and Specs A millisecond pulsar found by FAST
  16. 16. 21cm Cosmology • hyperfine splitting of neutral hydrogen (HI) ground state: 21cm transition • with redshift of Universe, wavelength becomes λ=21(1+z)cm • 21cm tomography: observations over a frequency range probe 3D structure • HI: before Epoch of Reionization (EoR), distributed over whole Universe, after EoR the gas between galaxies are ionized by UV photon background, only within galaxies remain neutral due to higher recombination rate with high density EoR post EoR
  17. 17. 21CMA Total Antennas: 80 x 127(10160) Baseline 2.74(EW) x 4.01(NS) km Field of view (NCP) : 100 sq deg Angular resolution : 4’ Frequency coverage : 70—200 MHz
  18. 18. Tianlai (Heavenly Sound) Pathfinder • A small pathfinder experiment to check the basic principles and designs, find out potential problems • 3x15x40m cylinders, 96 dual polarization receiver units • 16 x 6m dishes • observe 700-800MHz, can be tuned in 600-1420MHz • If successful: expand to full scale 120mx120m, 2500 units HI intensity mapping
  19. 19. Existing Space MissionExisting Space Mission ,, Dark matterDark matter search and Cosmic Ray Experimentssearch and Cosmic Ray Experiments Wukong dark matter search (DAMPE) Huiyan Hard X-ray (HXMT) Jinping Underground Lab (PandaX, CDEX) @Sichuan Yangbajing Cosmic Ray Experiment @Tibet
  20. 20. The DAMPE e+ e- spectrum DAMPE coll., Nature, 552, 63 (2017) H. Jin et al., arxiv:1712.00362 A fit with nearby subhalo DM annihilations
  21. 21. PandaX J.-P. Cheng et al., arxiv:1801.00587
  22. 22. Planned FacilitiesPlanned Facilities • SVOM(China-France): multi-wavelength (γ+optical) GRB satellite • Antarctica Observatory (2m optical+ 2m THz) • LHAASO: 1km2 array cosmic ray experiment (4410m, Sichuan) • AliCPT: CMB polarization experiment (in Ali, Tibet) • LOT: 12m optical telescope (candidate sites in Xinjiang, Tibet, and Sichuan) • QTT: 110m radio telescope (in Qitai, Xinjiang) • CSST: 2m space optical telescope (to launch 2023) • Space gravitational wave experiment (Taiji proposed by CAS, Tianqin proposed by Sun Yatsen Univ.) International Cooperation Projects: • SKA • TMT
  23. 23. AliCPT • CMB B-mode polarization may indicate primordial gravitational wave • AliCPT: collaborating with BICEP, using site in Ali, Tibet (5250m, 32o 18’ N) • minimum water vapor (PWV 1mm) • near town(30km) and airport(20km)
  24. 24. AliCPT1: small aperture (72cm) aim at l~100, TES bolometer+SQUIDs, 1704*4 detectors, frequency: 95GHz, 150 GHz First Light 2020, observing Mar-Oct. AliCPT-2: upgrade with 12 more modules Future: 6000m site (PWV~0.6mm) 2 small aperture covering more frequencies 1 medium aperture(4~6m)
  25. 25. Space Telescope • Part of the Chinese Space Station Program, 2m optical telescope • an independently flying module on the same orbit (not physically connected to the manned space station) • 7 band photometric survey17500 deg2 , iAB =26, galaxies:28/arcmin2 , • 3 band grism, R~200
  26. 26. Ultra-long wavelength satellite array • Below 10MHz, due to ionosphere absorption, ground observation is nearly impossible. • Dark Age & Cosmic Dawn may produce feature in 21cm global spectrum, recently EDGES claim detected such feature • But ionosphere and RFI may cause problems • Far side of Moon provide best environment for observations RAE-2 sky map (1979) Bowman et al., 2018
  27. 27. Discovering Sky at Longest (DSL) wavelength • Chang’e-4 mission provide opportunity for some pilot study • A future dedicated mission: linear array (5-8) of satellites moving around the moon, take observation at the backside of the moon, then transmit data back at the front side of the moon. • A mother satellite measure the position of the daughter satellites • Imaging sky below 30 MHz, and measure all sky average spectrum with high precision 30-120 MHz • Currently under intensive study (XC as PI), aim for mid-2020s launch Huang et al., arXiv:1805.08259
  28. 28. Summary • China has a wide variaties of ongoing researches in cosmology and astronomy. • Some notable theoretical results, e.g. the quintom dark energy model, holographic dark energy model, Eg test for modified gravity, etc. • So far most of the data used are from abroad, but new facilities are beginning to provide interesting results • Rapid progress in the construction and development of many astronomical facilities • Operational support and science research is somewhat inadequate, partly due to inefficient funding mechanism, partly due to lack of experienced personnel • Welcome to International Collaborations, including the Belt & Road cooperation program
  29. 29. I apollogize for those institutes, projects and people missed in this talk Thank You!

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